1. Field of Invention
This invention relates generally to electrical interconnection systems.
2. Discussion of Related Art
Electrical connectors are used in electronic systems to form connections between assemblies that are manufactured separately but exchange signals during operation. Frequently, the assemblies are formed with printed circuit boards (“PCBs”), each of which includes a connecter that mates with a complementary connecter on another one of the PCBs. A frequently used arrangement for interconnecting multiple PCBs is to have one PCB serve as a backplane. Other PCBs, which are called “daughter boards” or “daughter cards,” are then connected through the backplane by mating electrical connectors that intersect the backplane at a right angle, allowing connectors on the daughter boards to be inserted into connectors on the backplane. For this reason, the connectors used to connect daughter boards to a backplane are sometimes called “right angle connectors” or “backplane connectors.” Similar connectors may be used in electronic systems with midplanes to which daughter boards may be attached on two sides or in other systems in which boards intersect at a right angle.
Electrical connectors may also be used to join PCB's in other configurations. Some electronic systems include a “mother board,” which contains a processor or other electronic components. Components that interact with components on the mother board may be attached to a daughter board, which is frequently mounted parallel to the mother board. “Stacker” or “mezzanine” connectors may be used to join the boards in this configuration.
Other types of connectors may be used to join other types of assemblies. For example, cables, with cable connectors at one or both ends, may be used to join assemblies that do not directly intersect.
Regardless of the specific application, electronic assemblies frequently have connectors shaped to mate with connectors on other assemblies. When the connectors on the assemblies are mated, conducting paths are completed through the connectors, providing electrical connections between the assemblies. However, in some instances, subassemblies for which connections are desired may not have connectors configured to mate with each other. In this scenario, an adapter may be used.
An adapter may be an assembly with two or more connectors. One of the connectors may mate with a connector on one of the assemblies to be joined, and another connector on the adaptor may mate with a connector on another of the assemblies. The adapter may provide conducting paths between the two connectors so that points on one assembly that are connected to one of the connectors of the adapter are appropriately connected to points on the other assembly that are connected to the other connector of the adapter.
In some systems, merely routing signals from one connector of the adapter to another is not adequate to ensure proper functioning of the assemblies. For example, one assembly may output signals of a different type or in a different form than is required at the input of the other assembly. Accordingly, adapters may include components that modify signals as they pass through the adapter to ensure that each assembly receives signals in an appropriate form.
Regardless of the specific application of electrical connectors, a connector should have electrical and mechanical properties appropriate for the system in which it will be used. One of the difficulties in making a connector is that electrical conductors in the connector can be so close that there can be electrical interference between adjacent signal conductors. To reduce interference, and to otherwise provide desirable electrical properties, metal members are often placed between or around adjacent signal conductors. The metal acts as a shield to prevent signals carried on one conductor from creating “crosstalk” on another conductor. The metal also impacts the impedance of each conductor, which can further contribute to desirable electrical properties.
As signal frequencies increase, there is a greater possibility of electrical noise being generated in the connector in forms such as reflections, crosstalk and electromagnetic radiation. Therefore, electrical connectors for higher speed signals are designed to limit crosstalk between different signal paths and to control the characteristic impedance of each signal path. Shield members are often placed adjacent signal conductors in a connector for this purpose.
Although shields for isolating conductors from one another are typically made from metal components, U.S. Pat. No. 6,709,294 (the '294 patent), which is assigned to the same assignee as the present application and which is hereby incorporated by reference in its entirety, describes making an extension of a shield plate in a connector from conductive plastic. U.S. Published Application 2006/0068640 and U.S. Pat. No. 7,163,421, which are assigned to the assignee of the present invention and which are hereby incorporated by reference in their entireties, also describe the use of lossy material to improve connector performance.
Electrical characteristics of a connector may also be controlled through the use of absorptive material. U.S. Pat. No. 6,786,771, (the '771 patent), which is assigned to the assignee of the present application and which is hereby incorporated by reference in its entirety, describes the use of absorptive material to reduce unwanted resonances and improve connector performance, particularly at high speeds (for example, signal frequencies of 1 GHz or greater, particularly above 3 GHz).
Other techniques may be used to control the performance of a connector. Transmitting signals differentially can also reduce crosstalk. Differential signals are carried by a pair of conducting paths, called a “differential pair.” The voltage difference between the conductive paths represents the signal. In general, a differential pair is designed with preferential coupling between the conducting paths of the pair. For example, the two conducting paths of a differential pair may be arranged to run closer to each other than to adjacent signal paths in the connector. No shielding is desired between the conducting paths of the pair, but shielding may be used between differential pairs. Electrical connectors can be designed for differential signals as well as for single-ended signals.
Examples of differential electrical connectors are shown in U.S. Pat. No. 6,293,827 (the '827 patent) and U.S. Pat. No. 6,776,659 (the '659 patent), which are assigned to the assignee of the present application. Both the '827 patent and the '659 patent are hereby incorporated by reference in their entireties.